This disclosure relates to a probe card for electrical testing a chip in a wide temperature range, and more particularly, to a probe card for electrical testing a chip in a wide temperature range between −120° C. and 450° C.
FIG. 1 is a top view of a probe card 10 for testing a chip according to the prior art. The probe card 10 comprises a circuit board 12, a circular supporter 14 positioned on the circuit board 12, a plurality of probe needles 16 positioned on the circular supporter 14 and wires 18 connected to the end of the probe needle 16.
FIG. 2 is a cross-sectional diagram showing the probe card 10 applied to the electrical testing of a chip 36 of a wafer 30 according to the prior art. The semiconductor wafer 30 is positioned on a wafer chuck 32 with a heater 34, and comprises a plurality of chips 36. The probe needle 16 connects to a wire 26 on the backside of the circuit board 12 through a channel 20. The wafer chuck 32 will rise during testing so that the tip of the probe needle 16 can contact a pad 38 of the chip 36. The heater 34 will heat the semiconductor wafer 30 during testing, and heat will transmit to the probe card 10 by thermal radiation or by thermal conduction through the tip of the probe needle 16.
FIG. 3 is a close-up cross-sectional view of FIG. 2. The circular supporter 14 comprises an incline 28 and the included angle between the incline 28 and the surface of the circuit board is 7 degrees. Besides, the probe needle 16 is fixed on the incline of the circular supporter 14 by an epoxy resin 24.
In order to prevent the horizontal position of the probe needle 16 from shifting due to the increased usage time, it is necessary to use the epoxy resin 24 to fix the probe needle 16 on the circular supporter 14. According to the prior art, the probe needle 16 and the circular supporter 14 are made of tungsten, alloy of tungsten and rhenium, and ceramics. Since these materials can sustain high and low temperatures without deterioration, the technical bottleneck of the probe card 10 for high temperature testing is at the circuit board 12 and the epoxy resin 24. Additionally, since the material will expand and shrink with temperature variation, physical and chemical variations will occur in the material used in the probe card 10 and the structure of the probe needle 16 when testing is performed at relatively high and low temperatures. As a result, testing cannot be performed smoothly.
The probe card of the prior art causes the following drawbacks when testing is performed at very high or low temperatures:    (1) The circuit board cannot sustain high temperature: the circuit board used in the conventional probe card is made of polyimide or FR-4 with glass fiber. The working temperature of these materials is between 25° C. and 85° C., and the electrical properties of the probe card beyond 85° C. may be different from room temperature. Additionally, after high temperature testing for a long time, these fiber polymers will generate poisons which endanger the health of the operator and the high temperature will also deform the shape of the polymer which will dramatically influence the progress of testing.    (2) The position of the probe needle will shift: the probe card is the interface of a testing machine and a semiconductor sample, and the position of the probe needle is designed according to the position of the chip of the semiconductor sample so that several chips can be tested simultaneously. Consequently, the position of the probe needle dominates the accuracy of the testing. The material used in the conventional probe card only works at a temperature range between 25° C. and 85° C., and the thermal expansion coefficient is different from one material to another. When testing is performed at a temperature beyond the range the material can sustain, the material will deform due to the thermal expansion coefficient, and the horizontal position of the probe needle will seriously shift. Furthermore, the probe needle may peel off or curve so as to fail to work. Additionally, the angle of the conventional probe needle to the surface of the circuit board is 103 degrees, designed to meet the limit of the fixture. When the testing temperature is increased or decreased, this 103-degree will further cause shifting of the probe needle and serious damage.